Jamieson, Fausset and Brown on Isaiah 1:11

11. God does not here absolutely disparage sacrifice, which is as old and universal as sin (Ge 3:21; 4:4), and sin is almost as old as the world; but sacrifice, unaccompanied with obedience of heart and life (1Sa 15:22; Psa 50:9-13; 51:16-19; Ho 6:6). Positive precepts are only means; moral obedience is the end. A foreshadowing of the gospel, when the One real sacrifice was to supersede all the shadowy ones, and "bring in everlasting righteousness" (Psa 40:6, 7; Da 9:24-27; He 10:1-14).

full--to satiety; weary of

burnt offerings--burnt whole, except the blood, which was sprinkled about the altar.

fat--not to be eaten by man, but burnt on the altar (Le 3:4, 5, 11, 17).